Radio communications systems utilizing multiplexed noise codes are generally known. A typical example is shown and described in U.S. Pat. No. 4,293,953, entitled, "Bi-Orthogonal PCM Communications System Employing Multiplexed Noise Codes," which issued to Frank S. Gutleber, the present inventor, on Oct. 6, 1981.
The concept of code expansion and compression for the general class of multiplexed noise codes comprised of noise code mate pairs having autocorrelation functions which upon detection in a matched filter provide an impulse is also generally known. Such concepts are disclosed, for example, in U.S. Pat. No. 3,461,451, entitled, "Code Generator To Produce Permutations Of Code Mates", which issued to the present inventor on Aug. 12, 1969; U.S. Pat. No. 3,519,746, entitled, "Means And Methods To Obtain An Impulse Autocorrelation Function" which issued to the present inventor on July 7, 1970; and U.S. Pat. No. 3,634,765, entitled, "System To Provide An Impulse Autocorrelation Function . . . " which issued to the present inventor on Jan. 11, 1972.
In the above mentioned related application, U.S. Ser. No. 502,416, now abandoned, entitled, "Code Compressor For Interleaved Multiplexed Noise Codes", there is disclosed the concept of repetitively compressing corresponding code mate pairs in successive stages to provide ever diminishing codes of half the bit quantity and twice the amplitude until a single pulse results at the location of the final code bit whose amplitude is increased by a factor of twice the number of bits in each of the original interleaved codes. The apparatus employed comprises a series of cascaded code separators separated by delay lines providing ever increasing delays which are multiples of the pulsewidth of each code bit and wherein the delay is doubled at each stage until the last stage is reached and a delay of one half the original code length of the interleaved codes is provided, whereupon a combining of the codes results in an impulse autocorrelation function.
In the above referenced related application U.S. Ser. No. 551,431, entitled, "Multilevel Mate Pair Code Compressor For Codes Expanded By The Process Of Butting", there is disclosed the concept of compressing multilevel, multiplexed code mate pairs by repeatedly compressing corresponding code mate pairs in successive stages to provide diminishing codes of half the code length by amplifying the code mates by a predetermined amplification factor and then adding and subtracting the code mates in accordance with the following general rule: EQU A.sub.i-1 =A.sub.i +B.sub.i.sup.K.sbsp.i
and EQU B.sub.i-1 =A.sub.i.sup.K.sbsp.i -B.sub.i
where i is the i.sub.th compression stage and the exponent K.sub.i is the amplification factor for the i.sub.th stage. During the compression process, however, an ever decreasing time delay equal to half the input code width is provided so that the respective code mates generated by butting line up with one another in a time coincident relationship.
Accordingly, it is an object of the present invention to provide an improvement in the compression of noise codes.
Another object of the present invention is to provide an improvement in compression of multiplexed code mate pairs having more than one amplitude level.
Still another object of the invention is to provide an improvement in the compression of multilevel, multiplexed code mate pairs generated by the process of interleaving code mates.